The invention relates generally to the measurement of noise and more specifically concerns instrumentation for use in the measuring of aircraft noise and sonic boom.
This invention is an improvement in the invention disclosed in U.S. Pat. No. 3,868,856. The preceding invention was found excessively sensitive to changes in ambient temperature, owing to the pronounced temperature-sensitivity of the static microphone capacitance. The net effect of such changes is to detune the converter and reduce the conversion gain. The primary object of this invention is to develop automatic tuning compensation against changes in static microphone capacitance, in the face of severe temperature variations and other sources of long-term drift. Another object is to provide a remote electrical calibration capability, whereby an operator can calibrate the noise measurement system at a station located several thousand feet away from the microphone site.